In 1967, the Abatement Branch of the National Center for Air Pollution Control formed a group to undertake stack sampling. At that time, there was no standard system of stack sampling equipment which was directly applicable to the needs of the Branch. Thereafter, a system was designed to determine the amount of particulates or pollutants which are contained in an industrial stack. This system is used as the standard system as referenced in the Federal Register, Vol. 35, No. 247, Dec. 23, 1971, and is known as Method 5. Essentially, all Federally accepted data in support of New Source Performance Standards for particulate matter, and for determining compliance with particulate standards, is based upon this system. Commercially available equipment conforming to this EPA design is widely obtainable and is used for collecting the desired data. However, the sample box containing the fiber filter in this system contains much elaborate and delicate glass equipment thereby complicating the testing of the particulate matter. Furthermore, this sample box cannot be inserted through the standard three-inch or four-inch portholes which are contained in a great number of the stacks.
Many other methods and apparatus for measuring particulate emissions in a gas flow have been developed. One such apparatus is shown in U.S. Pat. No. 3,841,145 to Boubel. This apparatus, which comprises a stack sampler for collecting particulate samples in gaseous emissions, would appear at first glance to be quite similar to the present invention; however, there are very major and important differences. The Boubel device is a high-volume sampling system involving a number of components which together are used for extracting a large sample volume from a stack. This device is designed specifically to obtain a large sample of particulate matter in a short period of time, but is limited to those sources with emissions which are low in temperature and moisture content. While this device has merit for use on such sources, it is not equivalent to, and cannot satisfy the requirements which are essential in the EPA Standards.
Furthermore, since the Boubel device is a high-volume sampling system, the filter area which must be employed is of such a large size as to prohibit its insertion in the three- and four-inch standard ports, and therefore it must be used as an out of stack sampler. Additionally, the data collected from this Boubel out-of-stack filter cell, which cannot be subjected to high temperature emissions, would be different than that collected in an in-stack filter cell since the physical state of the emissions can be different in both filter cells.